The present invention broadly relates to adjustable chairs and, more specifically, pertains to a new and improved construction of an adjusting mechanism for a tiltable and vertically adjustable chair.
Generally speaking, the adjusting mechanism of the present invention serves for exerting a force on two components movable relative to one another and relates in particular to adjustable chairs comprising a cylinder and a piston displaceably guided therein with a piston rod conducted out of one front face of the cylinder, the piston subdividing the inner chamber of the cylinder into two partial cylinder chambers which are interconnected by at least one duct and are filled with a fluid medium.
In other words, the adjusting mechanism for exerting a force on first and second components moveable in relation to one another comprises a cylinder having a front face and defining an inner chamber, a piston displaceably guided in the cylinder and having a piston rod conducted out through the front face of the cylinder, the piston subdividing the inner chamber of the cylinder into two partial cylinder chambers, and there being further provided at least one transfer or locking duct interconnecting the two partial cylinder chambers. The two partial cylinder chambers are filled with a fluid medium.
Numerous different constructions of adjusting mechanisms of the aforementioned type are known and these are used in various different ways. A widely known construction of such an adjusting mechanism is constituted by the conventional gas spring. In its simplest construction, it comprises a cylinder, a piston guided therein and a piston rod connected to the piston. The inner chamber of the cylinder is filled with a fluid or flowable medium, e.g. a gas, which is under a certain pressure. The gas spring is arranged between two components movable towards one another, the cylinder being supported on one component and the piston rod on the other. In order to attain elastic or spring properties, the compressibility of the gas is exploited, the pressure in the cylinder rising approximately linearly when compressing the gas in the cylinder chamber. The gas spring is a relatively simple device, but high demands are made on the precision of its manufacture in order that the escape of gas on the surfaces movable relative to one another be as small as possible.
Another known type of adjustment device is constituted by the conventional shock absorber. The construction of a shock absorber is substantially the same as that of a gas spring, but oil or liquid is used as the fluid medium. A restricted channel or duct is provided in the piston and the oil is forced through the channel or duct during a relative movement of cylinder and piston and consequently the movement of the two parts is retarded, i.e. a damping or cushioning takes place.
One known use of the gas spring is in chairs with an adjustable seat or an adjustable back, or both. The function of the gas spring is to exert an opposing force on the seat or back, or both, when passing from the normal sitting position into a reclined or relaxed position and for elastically returning the chair to its normal position again.
However, it is also desirable for the chair to be fixable in an arbitrary position. To this end, corresponding devices are known in connection with the gas spring which enable the latter to be locked in specific positions. It is mainly due to the fluid medium or gas that it is difficult to lock the chair in a given position.